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Appl. Sci., Volume 9, Issue 14 (July-2 2019)

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Open AccessArticle
Virtual Object Manipulation by Combining Touch and Head Interactions for Mobile Augmented Reality
Appl. Sci. 2019, 9(14), 2933; https://doi.org/10.3390/app9142933 (registering DOI)
Received: 21 June 2019 / Revised: 18 July 2019 / Accepted: 19 July 2019 / Published: 22 July 2019
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Abstract
This paper proposes an interaction method to conveniently manipulate a virtual object by combining touch interaction and head movements for a head-mounted display (HMD), which provides mobile augmented reality (AR). A user can conveniently manipulate a virtual object with touch interaction recognized from [...] Read more.
This paper proposes an interaction method to conveniently manipulate a virtual object by combining touch interaction and head movements for a head-mounted display (HMD), which provides mobile augmented reality (AR). A user can conveniently manipulate a virtual object with touch interaction recognized from the inertial measurement unit (IMU) attached to the index finger’s nail and head movements tracked by the IMU embedded in the HMD. We design two interactions that combine touch and head movements, to manipulate a virtual object on a mobile HMD. Each designed interaction method manipulates virtual objects by controlling ray casting and adjusting widgets. To evaluate the usability of the designed interaction methods, a user evaluation is performed in comparison with the hand interaction using Hololens. As a result, the designed interaction method receives positive feedback that virtual objects can be manipulated easily in a mobile AR environment. Full article
(This article belongs to the Special Issue Augmented Reality: Current Trends, Challenges and Prospects)
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Open AccessArticle
Real-Time Implementation of an Expert Model Predictive Controller in a Pilot-Scale Reverse Osmosis Plant for Brackish and Seawater Desalination
Appl. Sci. 2019, 9(14), 2932; https://doi.org/10.3390/app9142932 (registering DOI)
Received: 21 May 2019 / Revised: 27 June 2019 / Accepted: 1 July 2019 / Published: 22 July 2019
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Abstract
This article addresses the design and real-time implementation of an expert model predictive controller (Expert MPC) for the control of the brackish and seawater desalination process in a pilot-scale reverse osmosis (RO) plant. This pilot-scale plant is used in order to obtain the [...] Read more.
This article addresses the design and real-time implementation of an expert model predictive controller (Expert MPC) for the control of the brackish and seawater desalination process in a pilot-scale reverse osmosis (RO) plant. This pilot-scale plant is used in order to obtain the optimal operation conditions of the RO desalination process through the implementation of different control strategies, as well as in the training of operators in the new control and management technologies. A dynamical mathematical model of this plant has been developed based on the available field data and system identification procedures. Predictions of the obtained model were in good agreement with the available field data. The designed Expert MPC is distinguished by having a plant identification block and an expert system. The expert system, using a rule-based approach and the evolution of the plant variables, can modify the plant identification block, the plant prediction model, and/or the optimizer in order to improve the performance, robustness and operational safety of the overall control system. The real-time comparison results of the designed Expert MPC and a well-designed model predictive controller (MPC) show that the proposed Expert MPC has a significantly better performance and, therefore, higher accuracy and robustness. Full article
Open AccessArticle
Multi-Robot Exploration Based on Multi-Objective Grey Wolf Optimizer
Appl. Sci. 2019, 9(14), 2931; https://doi.org/10.3390/app9142931 (registering DOI)
Received: 25 June 2019 / Revised: 17 July 2019 / Accepted: 17 July 2019 / Published: 22 July 2019
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Abstract
In this paper, we used multi-objective optimization in the exploration of unknown space. Exploration is the process of generating models of environments from sensor data. The goal of the exploration is to create a finite map of indoor space. It is common practice [...] Read more.
In this paper, we used multi-objective optimization in the exploration of unknown space. Exploration is the process of generating models of environments from sensor data. The goal of the exploration is to create a finite map of indoor space. It is common practice in mobile robotics to consider the exploration as a single-objective problem, which is to maximize a search of uncertainty. In this study, we proposed a new methodology of exploration with two conflicting objectives: to search for a new place and to enhance map accuracy. The proposed multiple-objective exploration uses the Multi-Objective Grey Wolf Optimizer algorithm. It begins with the initialization of the grey wolf population, which are waypoints in our multi-robot exploration. Once the waypoint positions are set in the beginning, they stay unchanged through all iterations. The role of updating the position belongs to the robots, which select the non-dominated waypoints among them. The waypoint selection results from two objective functions. The performance of the multi-objective exploration is presented. The trade-off among objective functions is unveiled by the Pareto-optimal solutions. A comparison with other algorithms is implemented in the end. Full article
(This article belongs to the Special Issue Mobile Robots Navigation)
Open AccessArticle
A Hybrid Approach Using Fuzzy AHP-TOPSIS Assessing Environmental Conflicts in the Titan Mining Industry along Central Coast Vietnam
Appl. Sci. 2019, 9(14), 2930; https://doi.org/10.3390/app9142930 (registering DOI)
Received: 1 July 2019 / Revised: 16 July 2019 / Accepted: 18 July 2019 / Published: 22 July 2019
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Abstract
Environmental conflict management gains significance in rational use of natural resources, ecosystem preservation and environmental planning for mineral mines. In Central Coast Vietnam, titan mines are subject to conflicting use and management decisions. The paper deals with an empirical research on applying a [...] Read more.
Environmental conflict management gains significance in rational use of natural resources, ecosystem preservation and environmental planning for mineral mines. In Central Coast Vietnam, titan mines are subject to conflicting use and management decisions. The paper deals with an empirical research on applying a combination of the fuzzy Analytic Hierarchy Process (AHP) and the fuzzy Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) to measure environmental conflicts emerging as a result of titan mining in Vietnam. The methodology used in the paper combines the fuzzy AHP and the fuzzy TOPSIS to rank environmental conflicts and propose conflict prevention solutions in the titan mining industry of Ky Khang coastal commune (Ky Anh district, Central Coast Vietnam). Data was collected by using a questionnaire with 15 locals, 8 communal authorities, 2 district authorities, and 12 scientific experts on titan mining, environmental geology, and sustainability management. The result shows that, titan mining conflicts with the eight criteria of economic sectors at five alternative sites including beach, protected forest, agricultural area, settlement area, and industrial area. The conflicts between titan mining and forestry, agriculture, settlements, fishing and aquaculture are highly valued. The beach area shows most environmental conflict as a result of titan mining, followed by the agricultural area and settlement area. Based on the empirical findings, legal and procedural tools such as environmental impact assessments, strategic environmental assessments, integrated coastal zone management, marine spatial planning, and multi-planning integration advancing environmental management for titan mines in Vietnam are suggested. Full article
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Open AccessArticle
Augmented Reality Implementations in Stomatology
Appl. Sci. 2019, 9(14), 2929; https://doi.org/10.3390/app9142929 (registering DOI)
Received: 3 July 2019 / Revised: 16 July 2019 / Accepted: 18 July 2019 / Published: 22 July 2019
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Abstract
Augmented reality has a wide range of applications in many areas that can extend the study of real objects into the digital world, including stomatology. Real dental objects that were previously examined using their plaster casts are often replaced by their digital models [...] Read more.
Augmented reality has a wide range of applications in many areas that can extend the study of real objects into the digital world, including stomatology. Real dental objects that were previously examined using their plaster casts are often replaced by their digital models or three-dimensional (3D) prints in the cyber-physical world. This paper reviews a selection of digital methods that have been applied in dentistry, including the use of intra-oral scanning technology for data acquisition and evaluation of fundamental features of dental arches. The methodology includes the use of digital filters and morphological operations for spatial objects analysis, their registration, and evaluation of changes during the treatment of specific disorders. The results include 3D models of selected dental arch objects, which allow a comparison of their shape and position during repeated observations. The proposed methods present digital alternatives to the use of plaster casts for semiautomatic evaluation of dental arch measures. This paper describes some of the advantages of 3D digital technology replacing real world elements and plaster cast dental models in many areas of classical stomatology. Full article
(This article belongs to the Special Issue Augmented Reality: Current Trends, Challenges and Prospects)
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Open AccessArticle
Address Space Layout Randomization Next Generation
Appl. Sci. 2019, 9(14), 2928; https://doi.org/10.3390/app9142928 (registering DOI)
Received: 2 June 2019 / Revised: 7 July 2019 / Accepted: 15 July 2019 / Published: 22 July 2019
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Abstract
Systems that are built using low-power computationally-weak devices, which force developers to favor performance over security; which jointly with its high connectivity, continuous and autonomous operation makes those devices specially appealing to attackers. ASLR (Address Space Layout Randomization) is one of the most [...] Read more.
Systems that are built using low-power computationally-weak devices, which force developers to favor performance over security; which jointly with its high connectivity, continuous and autonomous operation makes those devices specially appealing to attackers. ASLR (Address Space Layout Randomization) is one of the most effective mitigation techniques against remote code execution attacks, but when it is implemented in a practical system its effectiveness is jeopardized by multiple constraints: the size of the virtual memory space, the potential fragmentation problems, compatibility limitations, etc. As a result, most ASLR implementations (specially in 32-bits) fail to provide the necessary protection. In this paper we propose a taxonomy of all ASLR elements, which categorizes the entropy in three dimensions: (1) how, (2) when and (3) what; and includes novel forms of entropy. Based on this taxonomy we have created, ASLRA, an advanced statistical analysis tool to assess the effectiveness of any ASLR implementation. Our analysis show that all ASLR implementations suffer from several weaknesses, 32-bit systems provide a poor ASLR, and OS X has a broken ASLR in both 32- and 64-bit systems. This is jeopardizing not only servers and end users devices as smartphones but also the whole IoT ecosystem. To overcome all these issues, we present ASLR-NG, a novel ASLR that provides the maximum possible absolute entropy and removes all correlation attacks making ASLR-NG the best solution for both 32- and 64-bit systems. We implemented ASLR-NG in the Linux kernel 4.15. The comparative evaluation shows that ASLR-NG overcomes PaX, Linux and OS X implementations, providing strong protection to prevent attackers from abusing weak ASLRs. Full article
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Open AccessReview
Magnetic Nanomaterials for Magnetically-Aided Drug Delivery and Hyperthermia
Appl. Sci. 2019, 9(14), 2927; https://doi.org/10.3390/app9142927 (registering DOI)
Received: 31 May 2019 / Revised: 2 July 2019 / Accepted: 11 July 2019 / Published: 22 July 2019
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Abstract
Magnetic nanoparticles have continuously gained importance for the purpose of magnetically-aided drug-delivery, magnetofection, and hyperthermia. We have summarized significant experimental approaches, as well as their advantages and disadvantages with respect to future clinical translation. This field is alive and well and promises meaningful [...] Read more.
Magnetic nanoparticles have continuously gained importance for the purpose of magnetically-aided drug-delivery, magnetofection, and hyperthermia. We have summarized significant experimental approaches, as well as their advantages and disadvantages with respect to future clinical translation. This field is alive and well and promises meaningful contributions to the development of novel cancer therapies. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials for Drug Delivery and Therapy)
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Open AccessArticle
Synthesis and Diagnostics of Nanostructured Micaless Microcomposite as a Prospective Insulation Material for Rotating Machines
Appl. Sci. 2019, 9(14), 2926; https://doi.org/10.3390/app9142926 (registering DOI)
Received: 10 July 2019 / Accepted: 19 July 2019 / Published: 22 July 2019
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Abstract
This paper deals with the topic of composite insulation materials for rotating machines and it is primarily pointed to the synthesis of new three-component insulation system. In connection with this research, the basic components of the insulation system are selected and described by [...] Read more.
This paper deals with the topic of composite insulation materials for rotating machines and it is primarily pointed to the synthesis of new three-component insulation system. In connection with this research, the basic components of the insulation system are selected and described by different diagnostic methods. The proposed insulation material is composed of epoxy resin based on bisphenol-A diglycidyl ether, magnesium oxide nanofiller (1 wt %) with its own surface treatment technology using epoxysilane coupling agent ( γ -glycidoxypropyltrimethoxysilane) and polyethylene naphthalate as a reinforcing component. Following the defined topic of the paper, the proposed three-component insulation system is confronted with commonly used insulating systems (PET reinforced and Glass reinforced mica composites) in order to verify the basic dielectric properties (dielectric strength, volume resistivity, dissipation factor) and other parameters determined from phenomenological voltage and current signals, respectively. Full article
(This article belongs to the Section Nanotechnology and Applied Nanosciences)
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Open AccessReview
Graphene Composites for Lead Ions Removal from Aqueous Solutions
Appl. Sci. 2019, 9(14), 2925; https://doi.org/10.3390/app9142925 (registering DOI)
Received: 3 June 2019 / Revised: 15 July 2019 / Accepted: 15 July 2019 / Published: 22 July 2019
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Abstract
The indiscriminate disposal of non-biodegradable, heavy metal ionic pollutants from various sources, such as refineries, pulp industries, lead batteries, dyes, and other industrial effluents, into the aquatic environment is highly dangerous to the human health as well as to the environment. Among other [...] Read more.
The indiscriminate disposal of non-biodegradable, heavy metal ionic pollutants from various sources, such as refineries, pulp industries, lead batteries, dyes, and other industrial effluents, into the aquatic environment is highly dangerous to the human health as well as to the environment. Among other heavy metals, lead (Pb(II)) ions are some of the most toxic pollutants generated from both anthropogenic and natural sources in very large amounts. Adsorption is the simplest, efficient and economic water decontamination technology. Hence, nanoadsorbents are a major focus of current research for the effective and selective removal of Pb(II) metal ions from aqueous solution. Nanoadsorbents based on graphene and its derivatives play a major role in the effective removal of toxic Pb(II) metal ions. This paper summarizes the applicability of graphene and functionalized graphene-based composite materials as Pb(II) ions adsorbent from aqueous solutions. In addition, the synthetic routes, adsorption process, conditions, as well as kinetic studies have been reviewed. Full article
(This article belongs to the Special Issue Nanocomposites for the Sustainable Environment)
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Open AccessArticle
Performance Improvement for PMSM Driven by DTC Based on Discrete Duty Ratio Determination Method
Appl. Sci. 2019, 9(14), 2924; https://doi.org/10.3390/app9142924 (registering DOI)
Received: 27 May 2019 / Revised: 15 July 2019 / Accepted: 17 July 2019 / Published: 22 July 2019
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Abstract
In order to improve the performance of the servo control system, which is composed ofthe permanent magnet synchronous motor (PMSM) driven by novel direct torque control based on the fixed sector division criterion (FS-DTC) utilizing the composite active vectors, a discrete duty ratio [...] Read more.
In order to improve the performance of the servo control system, which is composed ofthe permanent magnet synchronous motor (PMSM) driven by novel direct torque control based on the fixed sector division criterion (FS-DTC) utilizing the composite active vectors, a discrete duty ratio determination method (FS-DDTC) is proposed in this paper. The determination of the accurate duty ratio is the key to obtain the desired error compensational results for PMSM, which is related to the performance of the servo system directly. As the applied master vector and slave vector during each control period are the adjacent vectors, therefore, the direction of the synthetic vector is between the directions of the two applied active vectors. Additionally, the analytical relationship between the sector angle of the synthetic vector and the error rate, which can realize the determination of the discrete duty ratio value without complicated calculations is deduced first. Furthermore, the duty ratio values of the two applied active vectors in FS-DTC are obtained through the selections of the duty ratio scale in the novel discrete duty ratio determination method directly, which can simplify the calculation process of the accurate duty ratio values effectively. The effectiveness of the proposed discrete duty ratio determination method is verified through the experimental results on a 100-W PMSM drive system. Full article
(This article belongs to the Section Energy)
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Open AccessFeature PaperArticle
Wind Resource Assessment on Puná Island
Appl. Sci. 2019, 9(14), 2923; https://doi.org/10.3390/app9142923 (registering DOI)
Received: 18 May 2019 / Revised: 16 July 2019 / Accepted: 17 July 2019 / Published: 22 July 2019
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Abstract
Puná Island, located in the Pacific Ocean off the southern coast of Ecuador, has a population of approximately 3344 inhabitants. However, not all inhabitants have access to electricity, which is largely supplied by diesel generators. Therefore, to identify a renewable, sustainable, environmentally friendly [...] Read more.
Puná Island, located in the Pacific Ocean off the southern coast of Ecuador, has a population of approximately 3344 inhabitants. However, not all inhabitants have access to electricity, which is largely supplied by diesel generators. Therefore, to identify a renewable, sustainable, environmentally friendly and low-cost alternative, a 40-m-high anemometer tower was installed for wind resource assessment and to determine the possibility of generating electricity from wind energy. Based on mathematical models for electricity generation from wind energy, data were analyzed using the software Windographer and WAsP, to determine a long-term wind speed of 4.8 m/s and a mean wind power density of 272 W/m2. By simulating the use of a 3.3-MW wind turbine, we demonstrated that as much as 800 kWh could be generated during the hours when the wind reaches its highest speed. In addition to demonstrating the technical feasibility of meeting the electricity demands of Puná Island through wind power, this study exemplifies a method that can be used for wind resource assessment in any location. Full article
(This article belongs to the Section Energy)
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Open AccessArticle
Using the Characteristics of Pulse Waveform to Enhance the Accuracy of Blood Pressure Measurement by a Multi-Dimension Regression Model
Appl. Sci. 2019, 9(14), 2922; https://doi.org/10.3390/app9142922 (registering DOI)
Received: 17 June 2019 / Revised: 12 July 2019 / Accepted: 18 July 2019 / Published: 22 July 2019
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Abstract
With the advancement of wearable technology, many physiological monitoring instruments are gradually being converted into wearable devices. However, as a consumer product, the blood pressure monitor is still a cuff-type device, which does perform a beat-by-beat continuous blood pressure measurement. Consequently, the cuffless [...] Read more.
With the advancement of wearable technology, many physiological monitoring instruments are gradually being converted into wearable devices. However, as a consumer product, the blood pressure monitor is still a cuff-type device, which does perform a beat-by-beat continuous blood pressure measurement. Consequently, the cuffless blood pressure measurement device was developed and it is based on the pulse transit time (PTT), although its accuracy remains inadequate. According to the cardiac hemodynamic theorem, blood pressure relates to the arterial characteristics and the contours of the pulse wave include some characteristics of the artery. Therefore, the purpose of this study was to use the contour characteristics of the pulses measured by photoplethysmography (PPG) to estimate the blood pressure using a linear multi-dimension regression model. Ten subjects participated in the experiment, and the blood pressure levels of the subjects were elevated by exercise. The results showed that the mean and standard deviation (mean ± SD) of the root mean square error of the estimated systolic and diastolic pressures within the best five parameters were 6.9 ± 2.81 mmHg and 4.0 ± 0.65 mmHg, respectively. Compared to the results that used one parameter, the PTT, for estimating the systolic and diastolic pressures, 8.2 ± 2.1 mmHg and 4.5 ± 0.79 mmHg, respectively, our results were better. Full article
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Open AccessArticle
An Automated ECG Beat Classification System Using Deep Neural Networks with an Unsupervised Feature Extraction Technique
Appl. Sci. 2019, 9(14), 2921; https://doi.org/10.3390/app9142921 (registering DOI)
Received: 25 June 2019 / Revised: 17 July 2019 / Accepted: 18 July 2019 / Published: 22 July 2019
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Abstract
An automated classification system based on a Deep Learning (DL) technique for Cardiac Disease (CD) monitoring and detection is proposed in this paper. The proposed DL architecture is divided into Deep Auto-Encoders (DAEs) as an unsupervised form of feature learning and Deep Neural [...] Read more.
An automated classification system based on a Deep Learning (DL) technique for Cardiac Disease (CD) monitoring and detection is proposed in this paper. The proposed DL architecture is divided into Deep Auto-Encoders (DAEs) as an unsupervised form of feature learning and Deep Neural Networks (DNNs) as a classifier. The objective of this study is to improve on the previous machine learning technique that consists of several data processing steps such as feature extraction and feature selection or feature reduction. It is also noticed that the previously used machine learning technique required human interference and expertise in determining robust features, yet was time-consuming in the labeling and data processing steps. In contrast, DL enables an embedded feature extraction and feature selection in DAEs pre-training and DNNs fine-tuning process directly from raw data. Hence, DAEs is able to extract high-level of features not only from the training data but also from unseen data. The proposed model uses 10 classes of imbalanced data from ECG signals. Since it is related to the cardiac region, abnormality is usually considered for an early diagnosis of CD. In order to validate the result, the proposed model is compared with the shallow models and DL approaches. Results found that the proposed method achieved a promising performance with 99.73% accuracy, 91.20% sensitivity, 93.60% precision, 99.80% specificity, and a 91.80% F1-Score. Moreover, both the Receiver Operating Characteristic (ROC) curve and the Precision-Recall (PR) curve from the confusion matrix showed that the developed model is a good classifier. The developed model based on unsupervised feature extraction and deep neural network is ready to be used on a large population before its installation for clinical usage. Full article
(This article belongs to the Special Issue ECG Signal and Its Applications)
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Open AccessArticle
Visualization of the Strain-Rate State of a Data Cloud: Analysis of the Temporal Change of an Urban Multivariate Description
Appl. Sci. 2019, 9(14), 2920; https://doi.org/10.3390/app9142920 (registering DOI)
Received: 11 June 2019 / Revised: 18 July 2019 / Accepted: 19 July 2019 / Published: 22 July 2019
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Abstract
One challenging problem is the representation of three-dimensional datasets that vary with time. These datasets can be thought of as a cloud of points that gradually deforms. However, point-wise variations lack information about the overall deformation pattern, and, more importantly, about the extreme [...] Read more.
One challenging problem is the representation of three-dimensional datasets that vary with time. These datasets can be thought of as a cloud of points that gradually deforms. However, point-wise variations lack information about the overall deformation pattern, and, more importantly, about the extreme deformation locations inside the cloud. This present article applies a technique in computational mechanics to derive the strain-rate state of a time-dependent and three-dimensional data distribution, by which one can characterize its main trends of shift. Indeed, the tensorial analysis methodology is able to determine the global deformation rates in the entire dataset. With the use of this technique, one can characterize the significant fluctuations in a reduced multivariate description of an urban system and identify the possible causes of those changes: calculating the strain-rate state of a PCA-based multivariate description of an urban system, we are able to describe the clustering and divergence patterns between the districts of a city and to characterize the temporal rate in which those variations happen. Full article
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Open AccessCommunication
Shape Memory Effect in Micro-Sized Shape Memory Polymer Composite Chains
Appl. Sci. 2019, 9(14), 2919; https://doi.org/10.3390/app9142919 (registering DOI)
Received: 6 June 2019 / Revised: 8 July 2019 / Accepted: 8 July 2019 / Published: 22 July 2019
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Abstract
Since the shape memory effect (SME) has been confirmed in micron and submicron sized polyurethane (PU) shape memory polymer (SMP), it might be used in novel micro/nano devices even for surgery/operation inside a single cell. In this study, micron sized protrusive PU SMP [...] Read more.
Since the shape memory effect (SME) has been confirmed in micron and submicron sized polyurethane (PU) shape memory polymer (SMP), it might be used in novel micro/nano devices even for surgery/operation inside a single cell. In this study, micron sized protrusive PU SMP composite chains are fabricated via mixing ferromagnetic nickel micro powders with PU SMP/dimethylformamide solution and then cured under a low magnetic field. Depending on the amount of nickel content, vertical protrusive chains with a diameter from 10 to 250 µm and height from 200 to 1500 µm are obtained. The SME in these chains is investigated to confirm the SME in SMP composites at microscale. An array of such protrusive chains may be utilized to obtain re-configurable surface patterns in a simple manner for applications, such as remarkable change in wetting and friction ability. Finally, its potential applications for micro electro mechanical systems (MEMS) and biomedical device are proposed. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Application of Hybrid Composites)
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Open AccessArticle
Congestion-Free Ant Traffic: Jam Absorption Mechanism in Multiple Platoons
Appl. Sci. 2019, 9(14), 2918; https://doi.org/10.3390/app9142918 (registering DOI)
Received: 11 June 2019 / Revised: 14 July 2019 / Accepted: 19 July 2019 / Published: 22 July 2019
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Abstract
In this paper, an agent-based model of ant traffic on a unidirectional single-lane ant trail is presented to provide better understanding of the jam-free traffic of an ant colony. On a trail, the average velocity of ants remains approximately constant irrespective of density, [...] Read more.
In this paper, an agent-based model of ant traffic on a unidirectional single-lane ant trail is presented to provide better understanding of the jam-free traffic of an ant colony. On a trail, the average velocity of ants remains approximately constant irrespective of density, thereby avoiding jamming. Assuming chemotaxis, we analyze platoon-related scenarios to assess the marching-platoon hypothesis, which claims that ants on a trail form a single platoon in which they march synchronously, thereby reducing hindrances due to increasing density. Contrary to that hypothesis, our findings show that ants on a trail do not march synchronously and do experience stop-and-go motion. However, more interestingly, our study also indicates that the ants’ chemotaxis behavior leads to a peculiar jam absorption mechanism, which helps to maintain free flow on a trail and avoids jamming. Again, contrary to the marching-platoon hypothesis, our findings also indicate that, rather than assisting traffic flow, forming a single cluster actually triggers jamming. Full article
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Open AccessArticle
Extracting Crop Spatial Distribution from Gaofen 2 Imagery Using a Convolutional Neural Network
Appl. Sci. 2019, 9(14), 2917; https://doi.org/10.3390/app9142917
Received: 25 May 2019 / Revised: 17 July 2019 / Accepted: 18 July 2019 / Published: 22 July 2019
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Abstract
Using satellite remote sensing has become a mainstream approach for extracting crop spatial distribution. Making edges finer is a challenge, while simultaneously extracting crop spatial distribution information from high-resolution remote sensing images using a convolutional neural network (CNN). Based on the characteristics of [...] Read more.
Using satellite remote sensing has become a mainstream approach for extracting crop spatial distribution. Making edges finer is a challenge, while simultaneously extracting crop spatial distribution information from high-resolution remote sensing images using a convolutional neural network (CNN). Based on the characteristics of the crop area in the Gaofen 2 (GF-2) images, this paper proposes an improved CNN to extract fine crop areas. The CNN comprises a feature extractor and a classifier. The feature extractor employs a spectral feature extraction unit to generate spectral features, and five coding-decoding-pair units to generate five level features. A linear model is used to fuse features of different levels, and the fusion results are up-sampled to obtain a feature map consistent with the structure of the input image. This feature map is used by the classifier to perform pixel-by-pixel classification. In this study, the SegNet and RefineNet models and 21 GF-2 images of Feicheng County, Shandong Province, China, were chosen for comparison experiment. Our approach had an accuracy of 93.26%, which is higher than those of the existing SegNet (78.12%) and RefineNet (86.54%) models. This demonstrates the superiority of the proposed method in extracting crop spatial distribution information from GF-2 remote sensing images. Full article
(This article belongs to the Special Issue Machine Learning Techniques Applied to Geospatial Big Data)
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Open AccessArticle
Theoretical Study of SOF2 Adsorption on Pd/Pt-Ni(111) Bimetallic Surfaces
Appl. Sci. 2019, 9(14), 2916; https://doi.org/10.3390/app9142916
Received: 19 June 2019 / Revised: 16 July 2019 / Accepted: 17 July 2019 / Published: 22 July 2019
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Abstract
Partial discharge has become a serious threat to the stable operation of gas-insulated switchgears. SOF2 is a characteristic decomposition component of SF6 decomposition components under partial discharge, which further deteriorate the severity of partial discharge. In order to find an excellent [...] Read more.
Partial discharge has become a serious threat to the stable operation of gas-insulated switchgears. SOF2 is a characteristic decomposition component of SF6 decomposition components under partial discharge, which further deteriorate the severity of partial discharge. In order to find an excellent adsorbent for SOF2, Pd/Pt-Ni(111) composite surface is raised as an adsorbent to investigate its adsorption ability of the SOF2 molecule. The results of the study show that Pd or Pt composite layer on Ni(111) atoms can significantly enhance the adsorption capacity, the adsorption ability to SOF2 is in the sequence of Pt-Ni(111) > Pd-Ni(111) > Ni(111) > Ni-Pd-Ni(111) > Ni-Pt-Ni(111). However, the adsorption of SOF2 on Pt-Ni(111) and Pd-Ni(111) surfaces is strong chemisorption, which is an irreversible adsorption process. On the contrary, Ni-Pd-Ni(111) and Ni-Pt-Ni(111) show moderate physisorption of SOF2. In addition, the density of electronic states, and electron density difference are further calculated to analyze the adsorption mechanism of SOF2. This research provides important theoretical support for developing an ideal SOF2 adsorbent. Full article
(This article belongs to the Section Nanotechnology and Applied Nanosciences)
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Open AccessArticle
Study on the Design and Cutting Performance of a Revolving Cycloid Milling Cutter
Appl. Sci. 2019, 9(14), 2915; https://doi.org/10.3390/app9142915
Received: 10 June 2019 / Revised: 16 July 2019 / Accepted: 17 July 2019 / Published: 21 July 2019
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Abstract
Problems such as low machining efficiency, severe tool wear and difficulty in safeguarding surface quality always exist in the machining process of titanium alloy with ball-end milling cutters. To address these issues, the design and manufacture of a revolving cycloid milling cutter for [...] Read more.
Problems such as low machining efficiency, severe tool wear and difficulty in safeguarding surface quality always exist in the machining process of titanium alloy with ball-end milling cutters. To address these issues, the design and manufacture of a revolving cycloid milling cutter for titanium alloy processing were studied in this paper. Firstly, the mathematical model of the revolving cycloid milling cutter contour surface was established. The parametric equation of an orthogonal helix cutting edge curve of a revolving cycloid milling cutter is presented. Then, the bottom boundary curve of the rake face is introduced. The five-axis grinding trajectory equation of revolving cycloid milling cutter rake face was derived based on the edge curve equation and coordinate transformation. Next, fabricating the revolving cycloid milling cutter and detecting the grinding accuracy of tool profile and geometric angle were performed. At last, a contrast test regarding the performance of the revolving cycloid milling cutter and the ball-end milling cutter in cutting titanium alloy TC11 was carried out. According to the test results, in comparison to the ball-end milling cutter, the revolving cycloid milling cutter had a smaller ratio of the axial force to the tangential force. Moreover, its flank face wore more slowly and evenly. As a result, a good surface processing quality can be maintained even under larger wear conditions, demonstrating an outstanding cutting performance. Full article
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Open AccessArticle
Empirical Formula to Predict the NOx Emissions from Coal Power Plant using Lab-Scale and Real-Scale Operating Data
Appl. Sci. 2019, 9(14), 2914; https://doi.org/10.3390/app9142914
Received: 29 May 2019 / Revised: 4 July 2019 / Accepted: 19 July 2019 / Published: 21 July 2019
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Abstract
The use of fossil fuels has drastically increased throughout the world as the demand for energy increases. Accordingly, it has become critical that we reduce the oxides of nitrogen (NOx) and oxides of sulfur pollutants. Therefore, studies related to these activities have increased. [...] Read more.
The use of fossil fuels has drastically increased throughout the world as the demand for energy increases. Accordingly, it has become critical that we reduce the oxides of nitrogen (NOx) and oxides of sulfur pollutants. Therefore, studies related to these activities have increased. This study was aimed at helping take pre-emptive action on NOx emissions by developing a formula that would predict NOx generation using factors related to the combustion characteristics and basic material properties of coal. In this study, the experiments were conducted using a drop tube furnace, and the correlation between coal’s major characteristics and NOx generation was analyzed and measured. Our results showed that the major factors affecting NOx generation are moisture, fixed carbon, and fuel ratio. Moisture tended to decrease NOx generation by delaying the ignition of coal and fixed carbon exhibited a tendency to be directly proportional to NOx generation. The R2 value for NOx of moisture and fixed carbon were derived as 0.7659 and 0.7063, respectively. Our results also showed that the fuel ratio had an exponential relation with the conversion of fuel-N to NOx. Based on the results of our analyses, we used moisture, fixed carbon, and fuel ratio as the major factors for creating an experimental formula. Through these results, we confirmed that the prediction formula reflects the actual amount of NOx emitted from the powerplants. Full article
(This article belongs to the Section Energy)
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Open AccessArticle
The Potential of Iron Ore Tailings as Secondary Deposits of Rare Earths
Appl. Sci. 2019, 9(14), 2913; https://doi.org/10.3390/app9142913
Received: 31 March 2019 / Revised: 17 July 2019 / Accepted: 18 July 2019 / Published: 21 July 2019
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Abstract
Rare earths have appeared in the market with new energy and Information Technology and Communications (ITC) applications. While their demand grows exponentially, their production is experiencing a bottleneck given that their deposits are concentrated in very few locations, mainly in China. This scarcity [...] Read more.
Rare earths have appeared in the market with new energy and Information Technology and Communications (ITC) applications. While their demand grows exponentially, their production is experiencing a bottleneck given that their deposits are concentrated in very few locations, mainly in China. This scarcity and dependence have turned them into strategic minerals, and the location of new sources has become vital. On the other hand, the inevitable trend towards sustainability favors the reuse of waste to avoid the degradation of new areas and the need for waste storage. One of the biggest generators of waste is iron mining. The tailings are stored in huge ponds with consequent environmental problems and risks. As tailings come from a concentration process, they incorporate different amounts of rare earths depending on their separation behavior. To evaluate the viability of these resources as potential repositories of rare earths, samples of different types of deposits and treatments were selected. The presence of different rare earths in them was determined through spectroscopy techniques to evaluate their use as a deposit. The results show an increase in the concentration of rare earths, especially high-density ones, which, although currently not economically feasible given the very wide geographical distribution of iron mining, represent a fundamental strategic reserve. Full article
(This article belongs to the Special Issue Concentrate Management and Resource Recovery for Sustainable Future)
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Open AccessArticle
Experimental Study on the Damping Effect of Multi-Unit Particle Dampers Applied to Bracket Structure
Appl. Sci. 2019, 9(14), 2912; https://doi.org/10.3390/app9142912
Received: 29 June 2019 / Revised: 12 July 2019 / Accepted: 18 July 2019 / Published: 20 July 2019
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Abstract
Particle damping (PD) is a passive mean of vibration control in which small metallic or ceramic particles are placed inside a cavity that attached to the primary structure at the place of high vibration amplitudes. The kinetic energy of the primary structure is [...] Read more.
Particle damping (PD) is a passive mean of vibration control in which small metallic or ceramic particles are placed inside a cavity that attached to the primary structure at the place of high vibration amplitudes. The kinetic energy of the primary structure is dissipated by non-elastic impact and friction between particles and walls. This paper represents a series of experimental investigations of the effects of multi-unit particle dampers (MUPD) attached to a bracket structure under harmonic excitation and random excitation. As a platform to investigate the particle damping characteristics under extreme acceleration environments, the bracket structure was featured by an extremely high response on the top, and its maximum acceleration exceeds 50 times gravity acceleration when the bracket structure was subjected to resonance. This broad range of acceleration conditions was far beyond the scope concerned in most previous work. The experimental results show that for a small weight penalty (no more than 8.8%), multi-unit particle damper can reduce the resonance of the primary structure by more than 50%, whether under sinusoidal excitation or random excitation. And the response of the primary structure depends on the type of cavities and filled coefficient. Layering the cavity in the direction of the main vibration can improve the damping capacity of the multi-unit particle damper. And the damper with small particle size and large number of features is suitable for vibration reduction under high acceleration conditions. Full article
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Open AccessArticle
Design and Experiment of a Moving Magnet Actuator Based Jetting Dispenser
Appl. Sci. 2019, 9(14), 2911; https://doi.org/10.3390/app9142911
Received: 12 June 2019 / Revised: 17 July 2019 / Accepted: 18 July 2019 / Published: 20 July 2019
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Abstract
Developing actuators to drive high-frequency jetting dispensers in the dispensing technology for electronic assembly applications has become a concern in recent years. This study proposed a new jetting dispenser without a displacement amplification mechanism directly actuated by a moving magnet actuator (MMA) to [...] Read more.
Developing actuators to drive high-frequency jetting dispensers in the dispensing technology for electronic assembly applications has become a concern in recent years. This study proposed a new jetting dispenser without a displacement amplification mechanism directly actuated by a moving magnet actuator (MMA) to jet small fluid droplets. In this article, the main geometric dimensions of the dispensing cluster including the needle, chamber, and seat-nozzle follow those of previous studies and existing dispensers to reduce design time. The necessary root-mean-square force applied to the dispenser needle, which is the key value for the MMA design, is calculated in detail. An ANSYS Maxwell finite element analysis (FEA) is used to simulate the MMA thrust force and modify geometric dimensions. The droplet size produced by the proposed dispenser is empirically investigated under various backpressure, operating frequency, needle displacement, and fluid temperature conditions. The experimental results indicated that the jet dispenser driven by the moving magnet actuator stably operated at the maximal operating frequency of 80 Hz. Some errors, such as losing droplets and generating small satellite dots around the main dots, did not occur during the operating process. In addition, the size of the proposal dispenser without the displacement-magnifying mechanism was also significantly reduced. To conclude, the jetting dispenser driven by the proposal moving magnet actuator can operate well at a medium frequency and shows great potential for dispensing technologies. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle
Reversible Data Hiding Scheme in Homomorphic Encrypted Image Based on EC-EG
Appl. Sci. 2019, 9(14), 2910; https://doi.org/10.3390/app9142910
Received: 25 June 2019 / Revised: 11 July 2019 / Accepted: 18 July 2019 / Published: 20 July 2019
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Abstract
To combine homomorphic public key encryption with reversible data hiding, a reversible data hiding scheme in homomorphic encrypted image based on EC-EG is proposed. Firstly, the cover image is segmented. The square grid pixel group randomly selected by the image owner has one [...] Read more.
To combine homomorphic public key encryption with reversible data hiding, a reversible data hiding scheme in homomorphic encrypted image based on EC-EG is proposed. Firstly, the cover image is segmented. The square grid pixel group randomly selected by the image owner has one reference pixel and eight target pixels. The n least significant bits (LSBs) of the reference pixel and all bits of target pixel are self-embedded into other parts of the image by a method of predictive error expansion (PEE). To avoid overflowing when embedding data, the n LSBs of the reference pixel are reset to zero before encryption. Then, the pixel values of the image are encrypted after being encoded onto the points of the elliptic curve. The encrypted reference pixel replaces the encrypted target pixels surrounding it, thereby constructing the mirroring central ciphertext (MCC). In a set of MCC, the data hider embeds the encrypted additional data into the n LSBs of the target pixels by homomorphic addition in ciphertexts, while the reference pixel remains unchanged. The receiver can directly extract additional data by homomorphic subtraction in ciphertexts between the target pixels and the corresponding reference pixel; extract the additional data by subtraction in plaintexts with the directly decrypted image; and restore the cover image without loss. The experimental results show that the proposed scheme has higher security than the similar algorithms, and the average embedding rate of the scheme is 0.25 bpp under the premise of ensuring the quality of the directly decrypted image. Full article
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Open AccessArticle
Hardware Prototyping and Validation of a W-ΔDOR Digital Signal Processor
Appl. Sci. 2019, 9(14), 2909; https://doi.org/10.3390/app9142909
Received: 21 June 2019 / Revised: 17 July 2019 / Accepted: 18 July 2019 / Published: 20 July 2019
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Abstract
Microwave tracking, usually performed by on ground processing of the signals coming from a spacecraft, represents a crucial aspect in every deep-space mission. Various noise sources, including receiver noise, affect these signals, limiting the accuracy of the radiometric measurements obtained from the radio [...] Read more.
Microwave tracking, usually performed by on ground processing of the signals coming from a spacecraft, represents a crucial aspect in every deep-space mission. Various noise sources, including receiver noise, affect these signals, limiting the accuracy of the radiometric measurements obtained from the radio link. There are several methods used for spacecraft tracking, including the Delta-Differential One-Way Ranging ( Δ DOR) technique. In the past years, European Space Agency (ESA) missions relied on a narrowband Δ DOR system for navigation in the cruise phase. To limit the adverse effect of nonlinearities in the receiving chain, an innovative wideband approach to Δ DOR measurements has recently been proposed. This work presents the hardware implementation of a new version of the ESA X/Ka Deep Space Transponder based on the new tracking technique named Wideband Δ DOR (W- Δ DOR). The architecture of the new transponder guarantees backward compatibility with narrowband Δ DOR. Full article
(This article belongs to the Section Electrical, Electronics and Communications Engineering)
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Open AccessArticle
Deep Homography Estimation and Its Application to Wall Maps of Wall-Climbing Robots
Appl. Sci. 2019, 9(14), 2908; https://doi.org/10.3390/app9142908
Received: 21 June 2019 / Revised: 13 July 2019 / Accepted: 17 July 2019 / Published: 20 July 2019
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Abstract
When locating wall-climbing robots with vision-based methods, locating and controlling the wall-climbing robot in the pixel coordinate of the wall map is an effective alternative that eliminates the need to calibrate the internal and external parameters of the camera. The estimation accuracy of [...] Read more.
When locating wall-climbing robots with vision-based methods, locating and controlling the wall-climbing robot in the pixel coordinate of the wall map is an effective alternative that eliminates the need to calibrate the internal and external parameters of the camera. The estimation accuracy of the homography matrix between the camera image and the wall map directly impacts the pixel positioning accuracy of the wall-climbing robot in the wall map. In this study, we focused on the homography estimation between the camera image and wall map. We proposed HomographyFpnNet and obtained a smaller homography estimation error for a center-aligned image pair compared with the state of the art. The proposed hierarchical HomographyFpnNet for a non-center-aligned image pair significantly outperforms the method based on artificially designed features + Random Sample Consensus. The experiments conducted with a trained three-stage hierarchical HomographyFpnNet model on wall images of climbing robots also achieved small mean corner pixel error and proved its potential for estimating the homography between the wall map and camera images. The three-stage hierarchical HomographyFpnNet model has an average processing time of 10.8 ms on a GPU. The real-time processing speed satisfies the requirements of wall-climbing robots. Full article
(This article belongs to the Special Issue Intelligent Robotics)
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Open AccessArticle
The Motivation of Technological Scenarios in Augmented Reality (AR): Results of Different Experiments
Appl. Sci. 2019, 9(14), 2907; https://doi.org/10.3390/app9142907
Received: 19 June 2019 / Revised: 12 July 2019 / Accepted: 17 July 2019 / Published: 19 July 2019
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Abstract
Augmented Reality (AR) is an emergent technology that is acquiring more and more relevance in teaching every day. Together with mobile technology, this combination arises as one of the most effective binomials to support significant and ubiquitous learning. Nevertheless, this binomial can only [...] Read more.
Augmented Reality (AR) is an emergent technology that is acquiring more and more relevance in teaching every day. Together with mobile technology, this combination arises as one of the most effective binomials to support significant and ubiquitous learning. Nevertheless, this binomial can only prove valid if the student is motivated to use it during the learning process. An attempt was made through the implementation of Keller’s Instructional Material Motivational Survey model o determine the degree of motivation of Pedagogy, Medicine and Art students from the University of Seville for using AR-enriched notes available by means of mobile devices in the classroom. Three applications designed for the subjects of Educational Technology, Anatomy and Art served to assess it positively in terms of the motivation raised by the participation in the experiment, as well as regarding academic performance improvement. It can additionally be stated that our main finding was a link between students’ motivation to use the enriched notes and the performance obtained in the subject in which they use them. Evidence was also found that the utilization of Augmented Reality benefits the learning process. Full article
(This article belongs to the Special Issue Augmented Reality: Current Trends, Challenges and Prospects)
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Open AccessArticle
Frequency Hopping Signals Tracking and Sorting Based on Dynamic Programming Modulated Wideband Converters
Appl. Sci. 2019, 9(14), 2906; https://doi.org/10.3390/app9142906
Received: 12 May 2019 / Revised: 2 July 2019 / Accepted: 12 July 2019 / Published: 19 July 2019
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Abstract
Most of the earlier tracking and network sorting approaches with a high sampling rate for frequency hopping (FH) signals did not adapt to the wideband system during their implementation, whereas the sub-Nyquist based algorithms cannot satisfy the real-time requirement for dealing with the [...] Read more.
Most of the earlier tracking and network sorting approaches with a high sampling rate for frequency hopping (FH) signals did not adapt to the wideband system during their implementation, whereas the sub-Nyquist based algorithms cannot satisfy the real-time requirement for dealing with the rapid change of sparsity. It is important to improve the compressed sensing (CS) methods for tracking and sorting wideband FH signals. In this paper, a dynamic programming modulated wideband converters (MWC) scheme is proposed. First, considering the wide gap of FH signals, an improved power estimation method is proposed to track the support set in the time domain. Second, to sort multiple signals more effectively, a feedback control algorithm based on dynamic programming is proposed. In the proposed method, the total sampling rate is decreased significantly, and multiple FH signals are separated rapidly without recovery based on the results of tracking and comparative power. Simulations show that the proposed method can track and sort FH signals efficiently and more practically than previous methods. Full article
(This article belongs to the Special Issue Recent Advances in Electronic Warfare Networks and Scenarios)
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Open AccessArticle
Performance Assessment of a Three-Dimensional Printed Porous Media Produced by Selective Laser Melting Technology for the Optimization of Loop Heat Pipe Wicks
Appl. Sci. 2019, 9(14), 2905; https://doi.org/10.3390/app9142905
Received: 16 June 2019 / Revised: 17 July 2019 / Accepted: 18 July 2019 / Published: 19 July 2019
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Abstract
The primary wick in a loop heat pipe device is a key component that is central to the operation of the device. Both high permeability and capillary pumping capacity, two properties highly dependent on wick structure, are strongly desirable for a satisfactory thermal [...] Read more.
The primary wick in a loop heat pipe device is a key component that is central to the operation of the device. Both high permeability and capillary pumping capacity, two properties highly dependent on wick structure, are strongly desirable for a satisfactory thermal performance. In this paper, selective laser melting (SLM), a three-dimensional (3D) printing technology, is used to create a primary wick for an 80 W heat transfer application. The permeability and capillarity values of this wick, experimentally measured, are compared with those built with the most widely used technologies nowadays, such as powder sintering and meshes. In this study, the SLM scaffold is shown to satisfy the minimum values required by the application in terms of capillarity and permeability: 0.031 mm/s and 4 × 10−12 m2, respectively. Our comparative study revealed that the wick produced with the SLM technology presented higher values of permeability, by two orders of magnitude, and slightly higher capillary figures than those corresponding to powder sintering for such application. However, it had capillary values well below those of a stainless-steel mesh. The hydraulic behavior of the SLM wick was better than that of the sintered copper powder, because it not only met the above-mentioned specifications, but it also improved its performance. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle
A Layer-Wise Strategy for Indoor As-Built Modeling Using Point Clouds
Appl. Sci. 2019, 9(14), 2904; https://doi.org/10.3390/app9142904
Received: 21 June 2019 / Revised: 11 July 2019 / Accepted: 12 July 2019 / Published: 19 July 2019
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Abstract
The automatic modeling of as-built building interiors, known as indoor building reconstruction, is gaining increasing attention because of its widespread applications. With the development of sensors to acquire high-quality point clouds, a new modeling scheme called scan-to-BIM (building information modeling) emerged as well. [...] Read more.
The automatic modeling of as-built building interiors, known as indoor building reconstruction, is gaining increasing attention because of its widespread applications. With the development of sensors to acquire high-quality point clouds, a new modeling scheme called scan-to-BIM (building information modeling) emerged as well. However, the traditional scan-to-BIM process is time-tedious and labor-intensive. Most existing automatic indoor building reconstruction solutions can only fit the specific data or lack of detailed model representation. In this paper, we propose a layer-wise method, on the basis of 3D planar primitives, to create 2D floor plans and 3D building models. It can deal with different types of point clouds and retain many structural details with respect to protruding structures, complicated ceilings, and fine corners. The experimental results indicate the effectiveness of the proposed method and the robustness against noises and sparse data. Full article
(This article belongs to the Special Issue LiDAR and Time-of-flight Imaging)
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